1. Field of the Invention
The invention relates to a digital adding device for determining the sum of a plurality of binary coded numbers, the device including a digital parallel-accumulator provided with a plurality of full adders corresponding to the plurality of bits of the numbers to be added and with a first memory storage element connected to outputs of the full adders for storing intermediate sums and intermediate carries resulting from the addition, the device also including a final adder for determining the sum of the numbers stored in the first memory storage element and, in addition, a circuit for coupling the final adder to the first memory storage element as well as a time control circuit for controlling the digital parallel-accumulator and the final adder.
2. Description of the Prior Art
Such a digital adding device is disclosed in U.S. Pat. No. 3,023,962.
The invention also relates to a digital filter including such a digital adding device.
Digital adding devices are used in digital filters, wherein an output codeword is formed as the weighted sum of a plurality of binary coded input codewords to be applied to the filter.
In the prior art digital adding device disclosed in U.S. Pat. No. 3,023,962 the total time required for determining a number of sums may be very long because forming a new sum cannot take place until the intermediate carry resulting from the addition has been able to exercise its influence on the final result and the final result has been read. In practice this means that, for example, when this prior art adding device is used in a digital filter the output frequency, that is to say the frequency with which the output codewords of the filter occur, is determined by both the number of input codewords to be weighted in an output codeword and the time required for having the carries exercice their influence on the final sum.
It is an object of the invention to provide a digital adding device of the type defined in the preamble in which the total time required for determining a plurality of sums is drastically reduced.